In many medical devices and particularly in ventilation tubes for intensive care, in ventilation tubes at the outlet of humidifiers and the like, it is conventionally necessary to heat the gaseous substance, generally air, that circulates inside the tube.
An electric resistor is currently used to solve the problem, said resistor being located inside the plastic tube, so as to heat the air to prevent condensation of the moisture contained therein.
This solution entails considerable drawbacks, since any burns caused by the electric resistor on the tube wall might generate fumes which would be fed to the patient, with the obvious associated problems.
Another drawback is also constituted by the fact that a resistor located. inside the tube is unable to provide for uniform heating of the inside walls of the tube and therefore cold spots may form which constitute condensation regions for the moisture that is present in ventilation cases, accordingly creating regions in which water accumulates and which, in addition to obstructing the useful cross-section of the tube, also constitute regions for bacterial growth.
In order to solve the above problem, ventilation tubes are already commercially available in which an external wire is provided which is wound in a spiral around the outer wall of the tube; this solution is considerably expensive and also causes problems, since it is necessary to provide for an additional tube in order to sheath the resistor, both owing to electrical insulation problems and in order to prevent excessively hot spots from remaining on the outside, possibly leading to problems for users.
This structure has the drawback that it is very heavy and that it considerably reduces the transparency, lightness and flexibility characteristics which are typical of a PVC tube.
Another drawback resides in the costs, since the sheathing of the tube, in addition to increasing the amount of plastics being used, requires much more complex and expensive production technologies than the ordinary spiral tube.